<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
		<style>
			* {
				margin: 0;
				padding: 0;
			}
			#container {
				margin: 10px 20px;
			}
			#container li {
				float: left;
				list-style: none;
				width: 60px;
				height: 60px;
			}
		</style>
	</head>
	<body>
		<div id="container">
			<img src="img/picture-1.jpg" alt="狗屎">
			<ul id="items">
				<li><img src="img/thumb-1.jpg" alt=""></li>
				<li><img src="img/thumb-2.jpg" alt=""></li>
				<li><img src="img/thumb-3.jpg" alt=""></li>
			</ul>
		</div>
		<script>
			var img = document.querySelector('#container>img');
			var images = document.querySelectorAll('#items img');
			for (var i = 0; i < images.length; i += 1) {
				// 事件回调函数在for循环的时候并没有执行所以也取不到循环变量i当前的值
				// JavaScript是动态弱类型语言可以在运行时动态的添加(或删除)对象的属性
				images[i].picture = 'img/picture-' + (i + 1) + '.jpg';
				images[i].addEventListener('mouseover', function(evt) {
					img.src = evt.target.picture;
				});
			}
		</script>
	</body>
</html>
